The purpose of this research is to determine the nature and properties of factors which effect the chemistry of calcium and phosphate ions in human salivary secretions. These fluids are supersaturated with respect to most basic calcium phosphate salts, but they lack the properties which are characteristic of metastable solutions. It has been found that saliva, and its macromolecular fraction, strongly inhibit precipitation from supersaturated solutions of calcium phosphate. Other complex protein mixtures, such as sera from humans and other mammals, are inactive. Salivary ultrafiltrates are also inactive, confirming the macromolecular nature of the active material. The acitivity of dialyzed parotid salivas from fifteen subjects varied significantly, the specific inhibitory activity, per unit of protein, varying by a factor of three. Unstimulated glandular secretions were active, but activity increased considerably on stimulation. Factors also exist in the saliva which inhibit transformation of dicalcium phosphate to more basic salts. Inhibitory material has also been extracted from dental plaque, and its presence there would strongly affect calculus formation. Present studies are aimed at determining the relationship between the salivary and plaque inhibitors. BIBLIOGRAPHIC REFERENCES: Gron, P., and Amdur, B.H.: The effect of topically applied fluoride on enamel remineralization in vitro. Arch. Oral Biol., 20: 223-224, 1975.